True inflatable boats have the advantages of lightness and collapsibility. However, they are deficient in sea-handling qualities. Rigid inflatables combine the features of soft inflatable gunwales, which provide floatation, with a solid "V" shaped hull that really improves the seaworthiness of the combined vessel.
Lightweight runabout motorboats are in demand as auxiliary craft to larger vessels. Both inflatables, and rigid inflatables are popular for this class of use. Major advantages of the pneumatic floatation tubes that surround both classes of boats are:
1. the pneumatic tubes act as "bumpers" when approaching docks and when the boats are hung on davits; PA1 2. the high level of floatation provided by having the pneumatic cylinders at the outermost sides of the gunwales allows passengers to sit out-board or exit by stepping off the gunwale. They also permit the easy retrieval of persons and objects from the water; PA1 3. the boat remains more upright in high seas, and during high speed turns; and PA1 4. this last feature is enhanced in boats of known design that incorporate a self-bailing water ballast tunnel that self-evacuates when the boat rises to planing speed. PA1 1. a rigid hull with a side portion terminating along its upper edge in a rigid gunwale, the gunwale having a load supporting deck portion along its outer periphery; PA1 2. a pneumatic tube-receiving longitudinal recess formed in said hull along the out-board side of the gunwale, beneath the deck; and PA1 3. a pneumatic tube fitted within the recess, the pneumatic tube being provided with coupling means;
In the latter case a deep hull is provided which, when the boat is near stationary, does not tend to float the pneumatic tubes out of, or up from, the water. The concept of the water ballast tunnel is shown in Norwegian patent 103822 issued in 1964 to Jan Linge.
Various means have been employed for fastening pneumatic floatation tubes to a boat. In U.S. Pat. No. 4,416,639 to Gillmer a standard sailing dingy is provided with a floatation collar or "pneumatic sponson". It is suggested that this tubing may be attached to the gunwale by glue, or embracing bands.
U.S. Pat. No. 4,750,448 to Hennebutte shows pneumatic side-stabilizing tubes that are inset into a partially embracing longitudinal recess running the length of the gunwale. Straps extending around the outer circumference of the tubes provide further security to ensure the retention of the inflated tubes within their longitudinal cowling. It is to be noted in the Hennebutte design that the rigid portion of the gunwale, constituting outboard decking extends overboard by about 45 degrees beyond the vertical. This design thereby limits the exposed bump-accommodating periphery of the tubing to a segment whose depth is about one-eighth of the tube's diameter. As well, when a person is pulled out of the water over this design of gunwale, they are mostly exposed to the more grating surface of the cowling, rather than the tube.
This same feature of an over-wrapping cowling that extends beyond the upper median line of the outer floatation tubes is similarly shown in U.S. pat. No. 3,261,038 to Klepper. Such an over-wrapping feature is presumably desirable in order to transfer lifting force generated by the floatation tubes to the ridges side walls and hull to which they are attached. Again Klepper employs external straps to retain the pneumatic tube in place within the longitudinal recess formed between the gunwale and boat hull.
As an alternate retention means a longitudinally aligned pin, which is adhesively bonded to the outer tube, fits within a mating recess or groove running along the under surface of the over hanging cowling. Such pin is not, however, engaged with the cowling but is merely pressed into it by pneumatic pressure.
While these and other examples of the prior art have endeavoured to combine pneumatic tubes with rigid hulls in varying ways, they have not done so in the manner of the invention hereafter described.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention will then be further described, and defined, in each of the individual claims which conclude this Specification.